1. Field of the Invention
The present invention relates to a gas boiler employing a bottom-up-type Bunsen burner combustion system. More particularly, the present invention relates to a heat exchange apparatus equipped with an exhaust gas guiding device for efficiently discharging exhaust gas and condensed water, in a waste heat collecting device for the gas boiler which collects waste heat generally produced after heat exchange with heating water through a sensible heat exchanger and then discharged as exhaust gas, through a latent heat exchanger, such that the thermal efficiency is improved, resulting in a reduction of gas consumption.
2. Description of the Related Art
In general, a gas boiler is structured to heat rooms or water as heat exchange is performed in such a manner that heat of exhaust gas produced by burning fuels, such as gas, is exchanged with heat of water, such as heating water, in a heat exchanger disposed at an upper part of a combustion chamber.
A combustion gas generated after the gas is burned in the gas boiler is supplied to perform heat exchange by passing through the heat exchanger and then discharged to the outside of the gas boiler as exhaust gas. Thus-discharged exhaust gas has a temperature lower than the initial temperature of the combustion gas.
Produced by burning of the gas in the gas boiler, the combustion gas is supplied to perform heat exchange through the heat exchanger, and is then discharged out of the gas boiler as exhaust gas. In this case, the exhaust gas has a temperature lower than the initial temperature of the combustion gas but higher than the room temperature. Therefore, there have been researches into a method for recycling a latent heat of the exhaust gas.
FIG. 1 shows a conventional gas boiler 10. Referring to the drawing, a waste heat collecting device 80 is mounted to an upper part of a combustion chamber 13 of the gas boiler 10.
The gas boiler 10 comprises a ventilator 11, a burner 12, the combustion chamber 13, a sensible heat exchanger 20, a duct 30, and a chamber 50 receiving a latent heat exchanger 60.
More specifically, the ventilator 11 is mounted at a lowermost end of the gas boiler 10, comprising a motor and a ventilation fan. The motor is rotated by external power application to drive external air into the gas boiler 10. The ventilation fan, rotated by a rotational force of the motor, draws in the external air through an opening fluidly communicated with the outside and then exerts a ventilation force for sending the external air through an opening fluidly communicated with the inside of the gas boiler.
The sensible heat exchanger 20 is disposed at an upper inside of the combustion chamber 13. Since the sensible heat exchanger 20 comprises a plurality of tubes 61 for circulation of heating water, the heating water is circulated by passing through tubes 62 of the latent heat exchanger 60 and then being supplied to the tubes 61 of the sensible heat exchanger 20.
The waste heat collecting device 80 comprises the duct 30 mounted to an upper part of the sensible heat exchanger 20, and also comprises the chamber 50, an exhaust guide 51, an exhaust hood 70, the latent heat exchanger 60, a drain 53, and a heat screen 40.
The duct 30 is mounted at an upper part of the sensible heat exchanger 20 of the combustion chamber 13. A Venturi member 31 is formed inside the duct 30 to increase flow velocity of the exhaust gas passing therethrough, such that the exhaust gas supplied from the combustion chamber 13 moves faster than at first when reaching an outlet of the duct 30. Additionally, an inside of the duct 30 is in the form of a double-wall and stuffed with an insulating material so as to restrain undesirable loss of heat at the duct 30 as much as possible.
The chamber 50 has a box form with an opened top side and closely contacts an upper end of the duct 30. The heat screen 40, being interposed between a lower end of the chamber 50 and the upper end of the duct 30, seals a connection part between the duct 30 and the chamber 50 while interrupting unnecessary thermal conduction.
A double heat exchange has been suggested as a method for recycling the latent heat of the exhaust gas. According to this, the exhaust gas is heat-exchanged in the sensible heat exchanger which performs heat exchange by heat of an initial combustion gas, and then heat-exchanged again in the latent heat exchanger disposed at the upper part of the sensible heat exchanger. Thus, the heat exchange between the combustion gas and the exhaust gas is performed first in the sensible heat exchanger and second in the latent heat exchanger. However, since the exhaust gas is directly discharged to the outside through the exhaust hood, the thermal efficiency is not satisfactory.
Also, according to the double heat exchanging method, during heat exchange in the sensible heat exchanger, condensed water generated in the respective tubes serving as paths for the heating water falls to the sensible heat exchanger, thereby deteriorating the thermal efficiency of the sensible heat exchanger. Furthermore, moisture and a nitric oxide contained in the condensed water may infiltrate the sensible heat exchanger and other electronic equipments, thereby damaging the equipments, for example, by causing corrosion.
In addition, since the latent heat exchanger is mounted directly above the sensible heat exchanger, there occurs a temperature difference between the sensible heat exchanger wherein relatively high-temperature heat exchange is performed and the latent heat exchanger wherein relatively low-temperature heat exchange is performed. Such a temperature difference between the sensible heat exchanger and the latent heat exchanger causes heat transfer or thermal flux. As a result, the thermal efficiency of the both heat exchangers is deteriorated.
As the above problems are caused by the relative positions between the sensible heat exchanger and the latent heat exchanger, there has been recently developed a double heat exchanger constructed by mounting a latent heat exchanger at the outside of a sensible heat exchanger. More specifically, the double heat exchanger is structured in such a manner that a burner is mounted to an upper part of a boiler in accordance with a double structure of the heat exchangers. According to this structure, heat generated from the burner is moved down through the center of the sensible heat exchanger and exchanged with heat of the sensible heat exchanger. Additionally, as exhaust gas heat-exchanged in the sensible heat exchanger is moved upward through the latent heat exchanger mounted at the outside of the sensible heat exchanger, heat exchange is performed again. However, because the sensible heat exchanger and the latent heat exchanger are exposed directly to the heat of the burner, all component parts of the heat exchangers are required to have high thermal resistance, thereby increasing the manufacturing cost and complicating the assembling process.